1. Field of the Invention
This invention relates to an improved crystal refining apparatus.
2. Prior Art
In the crystal refining apparatus of the prior art, for instance, disclosed in the Japanese laid open 87-244402 (Kokai Sho 62-244402), the amount of separated liquid containing impurities extracted from the refining column is dependent on the head difference between the inside and the outside of the refining column, so that the amount of separated liquid by extraction is limited to this extent. Accordingly, the value of the reflux ratio (defined as descending return flow rate inside the refining column /upflow rate of the solid crystal inside the refining column) can not be large enough and, consequently, it is very difficult to obtain highly refined crystal.
An objective of this invention, therefore, is to solve the afore mentioned defects of the conventional crystal refining apparatus and to provide a refining apparatus having a high reflux ratio (defined as descending return flow rate inside the refining column / upflow rate of the solid crystal inside the refining column) and capable of obtaining highly refined crystal.
Another objective of this invention is to provide a crystal refining apparatus which simultaneously can provide washing, sweating and recrystallization when needed, for obtaining highly refined crystals from crude crystals in a short period of time.
Upon further study of the specification and appended claims, further objectives and advantages of this invention will become apparent to those skilled in the art.